"I let him know the US is at a crossroads," Haley told reporters after her meeting with President Salva Kiir, "and every decision going forward was going to based on his actions."
South Sudan is the world's youngest country, having gained independence from Sudan in 2011. But despite high hopes and significant international support, the sub-Saharan African nation has been embroiled in a violent civil conflict for nearly its entire existence.
For several years, soldiers loyal to Kiir have clashed with forces loyal to his ousted vice president, Riek Machar, displacing millions of civilians. The two groups are largely split along ethnic lines.
"I told him that he couldn't deny the stories of his military, whether it was with violence, or with rape or child soldiers," Haley said of the meeting.
"His words don't match his actions"
Haley said she presented Kiir with a "tough list" of changes that the United States expects to see implemented going forward, which includes allowing full and consistent access for aid workers in the country. She said she pushed a specific timeline for these changes, but would not elaborate on the timeline publicly.
"He got what I was going to say," she said. "He understood this was a tough message. He understood that the United States was very disappointed in his leadership, I made that quite clear."
"And he understood all the aid or help that he hopes will go forward is not a given," she added, noting that the US has invested over $11 billion in South Sudan and is "now questioning that investment."
Haley, who is the first Cabinet-level official in the Trump administration to visit sub-Saharan Africa, said the one-on-one meeting was "private, candid," and punctuated by an "intense back and forth that was meaningful to both of us in the hope of making a better South Sudan."
Despite the "tough message," Haley seemed somewhat hopeful. She said the Kiir's demeanor did not match his defiant tone in a recent Washington Post interview
, during which he dismissed US threats to withhold aid and said the Trump administration has been fed misinformation about the conflict.
"I told him he couldn't deny the situations that we have seen and witnessed," Haley said. "He didn't try and deny them, but to his credit he acknowledged everything I was saying. He listened to everything I was saying and he was not defensive. Not at all."
After her meeting with Kiir, Haley visited a camp for displaced civilians in the South Sudan capital, Juba. That visit was interrupted by hundreds of anti-Kiir protestors, who shouted "Down with Salva Kiir," "Salva Kiir is a killer," and "Welcome Donald Trump."
Some held signs with Trump's picture, including one that read, "IDPs (internally displaced people) and refugees love President Trump, the peacemaker and supporter of human rights."
But the protests became rowdy, with demonstrators surrounding the area of the camp where Haley was meeting with a displaced family. Her party was quickly escorted to cars, ending the visit ahead of schedule.
On Tuesday, Haley visited a refugee camp in the neighboring Gambella region of Ethiopia, where nearly 400,000 refugees have fled to escape the South Sudan conflict.
Following the visit, Haley said the US bears an important responsibility to push for an end to the conflict, and described the pain experienced by the refugees as "just inconceivable."
The conflict in South Sudan has been marked by brutal attacks on civilians, including sexual violence against women. Some parts of the country have experienced famine, and the swelling refugee crisis is now reminiscent of what happened after the Rwandan genocide, with 4 million people, one third of the population, displaced from their homes.
On Wednesday, Haley said she told Kiir, that she "wanted to see him lead and lead all of his people."
"And that means they can't go hungry, they can't be abused, and can't be raped," she said. "Children can't be abducted."
"He made some promises," said Haley, "but he knows now he has to deliver."